Syngas-biomethanation in pressurized column: gradual increase in syngas flow rate leads to high methane productivity
Résumé
In a circular economy approach, heterogeneous wastes can be converted to syngas by pyro-gasification. The produced syngas can then be upgraded to methane to make use of the existing natural gas infrastructures. In this work, we report the performance of a biomethanation process to produce methane from syngas at high pressure and high syngas load.
Experiments were performed in a 10L continuous stirred tank reactor at 4 bars and 55°C. A syngas mixture (40% CO, 40% H2 and 20% CO2) was injected continuously. The inlet flow rate was gradually increased in steps of 20% from 7.5 NL/h to 56.5 NL/h. Methane productivity increased from 6.2 mmolCH4/Lreactor/h to 38.5 mmolCH4/Lreactor/h, which is to our knowledge the highest methane productivity obtained with syngas iomethanation. The conversion efficiencies dropped accordingly from 95% to 82% for CO and from 97% to 89% for H2. This drop in conversion efficiencies is attributed to mass transfer limitations. The 20% increase strategy allowed for biomass concentration to increase gradually and methane production was not interrupted when at each flow increase.
These results are very encouraging for syngas biomethanation, since methane productivity as high as 1 LCH4/Lreactor/h was obtained with our reactor which was not optimized in terms of mass transfer. This shows great promise for the future of the technology and is a remarkable step towards the industrialization of the process.